The present invention relates to a seat including a suspension system for lift trucks and other vehicles which must operate in low-overhead environments. In particular, the invention relates to a low profile spring suspended seat for a lift truck which provides superior support and resiliency characteristics in an unusually compact structural package.
Most modern commercial vehicles are provided with operator seats consisting of various arrangements of coils, springs and padding which compress, in linear fashion, with downward thrusts of an operator's body during use of the vehicle. The size and spring coefficients of such coil springs are usually traded off against operator comfort to provide seats with reasonable dimensions and ride characteristics.
However, such conventional systems are often impractical for use in lift trucks and other vehicles which often must operate in very low-overhead environments such as mine shafts, warehouse storage areas and the like. In such environments, operator seats must have very low profile configurations and this is usually achievable only at the expense of operator comfort and support. While low overhead environments serve as a consideration for desiring compactness of seats, this is not the only consideration. Actually, compactness is desirable with application to standard lift trucks and the intention is to meet the needs of standard lift trucks as well. The vertical dimension between the top of the vehicle body and the top of the overhead guard, less than the seated human operator height allowance, determines the maximum vertical height of the lift truck seat. Since the height available with lift trucks of less than 10,000 pounds capacity is so small, many of these lift trucks do not use suspension seats. Some use merely foam filled cushions.
Some attempts have been made in the prior art to address the pursuit of compact, yet resilient and supportive vehicle seat assemblies. Examples of such prior art attempts are found in U.S. Pat. Nos: 3,268,200; 3,319,920; 3,335,996; 3,325,136; 2,562,041; 3,572,828; and 3,601,351, to Eicher; Freedman et al; Hall et al; Radke, et al; Keller, et al; Lehner; and Ambrosino, respectively. None of such patents, however, disclose inventions specifically intended to provide comfortable, resilient support for the operator of a lift truck with a compact, low profile seat assembly including both flat and torsion springs in series combination coupled with parallel disposed frame support links.
The present invention provides such a lift truck seat suspension and does so with a minimum of expensive structural components and assembly and maintenance requirements. The resultant seat suspension is both inexpensively fabricatable and highly efficient in operation.